We request funds to acquire a 9.4-tesla Fourier transform ion cyclotron (FTJCR or FTMS) resonance mass spectrometer for two long term objectives, 1) improve the capability of FTMS for high-resolving-power detection of high-mass-to-charge ions and 2) apply the instrument to significant problems in the biomedical sciences. With regard to basic FTICR instrumental development, our specific aims are to: a) fabricate and implement an optimally designed electrically compensated trap; and b) implement a high trap pressure operating mode ("rf-only mode event") to allow ion storage and manipulation at orders of magnitude higher pressure (up to 0.01 torr) than currently possible in the FTMS mode. With regard to applying the instrument to significant problems in the biomedical sciences, our specific aims are: a) pursue an immunological investigation of antigen processing and presentation and identify those antigens implicated in type I diabetes; b) conduct research on DNA damage by UV radiation and estrogen carcinogens by investigating model oligodeoxynucleotides and their interactions with proteins and carcinogens to detect putative biomarkers of breast and prostate cancer; and c) study protein folding and noncovalent interactions by HID exchange at micromolar and lower concentrations. These two long-term objectives will be pursued by configuring the instrument so that the necessary hardware for instrumental development and biomedical applications can be rapidly switched (fraction of an hour) from one to another. We propose immediate application of the instrument to the three specific aims in biochemistry and medicine outlined above using state-of-the-art technology and transferring those applications to the more powerful instrument that will evolve as our instrumental development program proceeds.